Timing means for x-ray apparatus



Aug. 16, 1938. E. R. GOLDFIELD 2,126,957

TIMING MEANS FOR X'RAY APPARATUS Filed Jan. 2, 1937 6 FIG. I

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INVENTOR EDWIN R. GOLDFIELD TTORN Y6 I Patented Aug. 16, 1938 UNITED STATES PATENT OFFICE TIMING MEANS FOR X-RAY APPARATUS Application January 2, 1937, Serial No. 118,756

5 Claims.

This invention relates to means for controlling the operation of an X-ray tube and more particularly to means for limiting the time of tube operation.

In fiuorcscopy it is important to limit the total time of exposure of a patient, at the same time providing separate periods of exposure with intervals therebetween, and to this end it is an object of this invention to provide means which may be preset by the operator to limit the total time of tube operation and thus of exposure, while permitting interruption of operation at the will of the operator. Another object is to provide signal means for indicating the expiration of the predetermined operating period.

Frequently in practice a number of patients aremet in succession, the time limit upon each of which is identical, and a further object of the invention is to provide convenient stop means for similarly presetting the same time limit for such number of patients in succession. Further the invention embraces novel provision against accidental shifting of such stop means, to improve the safety of the apparatus which, of course, is operated largely in av dark room. Another object is to provide that the presetting of the time limit may be made at one location, whereas the independent exposures may be controlled thereafter by the operator at another location, as adjacent the fluoroscopic screen.

While the invention is particularly adaptable to fiuoroscopy, it might also be employed to advantage in connection with X-ray therapy as will be apparent to one familiar with the art.

The exact nature of this invention together with further objects and advantages thereof will be apparent from the following description taken in connection with the accompanying drawing, in which Fig. 1 is a conventionalized view showing diagrammatically apparatus illustrative of the invention; Fig. 2 is a face view of the time limiting unit showing the parts in a diiferent position from that of Fig. 1; Fig. 3 is a detail of parts appearing in Fig. 1 taken as in the plane of line 3-3, Fig. l; and Fig. 4 is an enlarged detail partly in section, showing the parts positioned as in Fig. 1.

With reference now to the drawing, A is an X-ray tube served through the usual high tension transformer I supplied with alternating current from the line L1, L2, through the operating circuit illustrated and including a relay switch 2 and auto-transformer 3, the relay switch being preferably employed for the usual reasons and, also as usual, located in series relation with the primary winding of the transformer l and the function of the transformer 3 being to supply a low voltage current for energizing the coil 2a of the relay switch 2 to close the latter and thus permit energization of the tube A, subject to the means to be described.

For control of the coil 2a a pair of switches 4 and 5 are arranged in series relation therewith in a control circuit as indicated in the drawing, so that the coil will be energized and the switch 2 thus closed, only when both the control switches 4 and 5 are closed, the control circuit then being closed from the tap of the transformer 3 through switch 4, switch 5, coil 2a and back to the near end of the transformer.

The switch 4 may be located convenient for control by the operator as adjacent the fluoroscopic screen to be employed in connection with the tube A. It may be of a pedal operated type closed by foot pressure and spring balanced to open position.

The switch 5 is a sensitive normally closed one having a plunger 5a, pressure upon which will open the switch and upon release of which plunger the switch will automatically reclose. Further details of the switch are not important here.

This switch 5 is arranged to be opened automatically to serve as a time limit switch and to this end a synchronous motor 6 is connected in parallel relation with the coil 2a as indicated in Fig. 1, so that the motor will operate coincidently with energization of the coil 2a and consequent energization of the tube A.

For immediate control of the switch 5, a cam I is provided having a lobe la capable of pressing the plunger 5a to open the switch 5 acting through a spring 51) so that the switch will be opened or closed dependent upon the position of the cam 1. Means are provided for driving the cam l by the motor 6 to open the switch 5, such means including a connection generally indicated at 8 and preferably reduction gearing conventionally indicated at 9, the motor driving the gearing and the latter driving the cam through the device 8.

The driving device 8 is of such nature that it will provide timed drive of the earn 1, clockwise, Fig. 2, and will permit adjustment of the cam relative to the motor, in the opposite direction. In the drawing a spring 8a bearing the friction disc 81) against the cam, is indicated for the purpose.

Conveniently the motor 6, switch 5, and described parts interconnecting them, are enclosed within a housing l0. For adjustment of the cam I from Without this housing, a knob l I is provided outside the housing and positively connected with the cam I as by a shaft Ila, so that the cam may be adjusted by the operator, against the friction device 8 and thus independent of the motor '6. The knob ll carries a pointer Ilb which moves over a scale upon the face of the housing I0, the pointer I lb being so related to the lobe Id of the cam I, and the scale being so calibrated as in minutes, with respect to the speed of the motor 6 and reduction provided by the gearing 9, and the parts being otherwise so proportioned and arranged, that time units are accurately indicated to the operator and that when the pointer llb indicates zero on the scale, the cam I will close the switch 5.

Signal means may be provided, for indicating opening of the switch 5 when the switch 4 is closed. Such means is here shown as a neon tube I4, located to be visible to the operator, and connected in the circuit in parallel relation to the switch 5.

Stop means are provided for positively limiting adjustment of the knob I I from its zero position. For this purpose as here shown a plate I2 is secured on the face of the housing Ill, having a series of notches I2a. A stop lever I3 is mounted for free movement on the shaft Ila beneath the knob ll having an upturned lug l3a engageable by the pointer I lb of the knob I l, having a finger I32) engageable in one of the notches I211, and having an upturned handle part I30.

The stop I3 is of spring material so that it yieldably maintains its finger I 3b in whatever notch l2a the latter may be positioned. Adjustment of the stop to another notch thus requires a sequence of motions in different directions, first outwardly from the housing In to withdraw its finger I31) and then about the shaft Ila. It is to be noted therefore that the stop is positively positionable by any of the notches I 2a, is practically incapable of accidental displacement when so positioned yet can easily be shifted when such is the operators desire.

Operation of the apparatus will be as follows, commencing with the switch 4 open, the knob l l in zero position and the line L1, L2, connected to a suitable source of alternating current supply. The switches 2 and 5 are now open, neither the motor 6 nor the tube A being in operation.

The operator having determined what maximum total exposure from the tube A is safe for the instant patient, sets the knob II and its stop I3 correspondingly. For example, in Fig. 2 of the drawing the stop is indicated as located for a 3-minute total exposure. It is convenient for the operator to first so set the stop and then simply move the knob ll up to the stop. Such adjustment of the knob moves the cam 1 against the friction device 8, permitting the switch 5 to close. The apparatus is then preset for the desired fluoroscopy.

The operator having suitably arranged his patient and being now located adjacent the switch 4, when operation of the tube is desired simply closes the switch 4 for so long a time as one exposure is desired. The switch 5 being already closed, closing of the switch 4 completes the circuit for the coil 2a, closes the switch 2 and causes opertion of the tube A. Instantly the tube begins to operate, so does the motor 6 driving the cam I toward its zero position.

When the operator opens the switch 4, the tube A and motor 6 are both deenergized, leaving the cam I to whatever position it may have been moved dependent upon the time of the exposure. As shown in Fig. 2, such exposure has been slightly over 1 minutes, leaving slightly under 1% minutes remaining for other exposures of the same patient.

When the operator is ready for his next exposure he again closes the switch 4 i or so long a time as desired, the parts operating as before.

When the maximum total preselected time has been exhausted by the several exposures, the cam I opens the switch 5, deenergizing the tube A independent of the switch 4, by deenergizing switch 2, and the operator knows that the time limit of exposure has expired. The switch 5 thus acts as an automatic limit switch for total time whereas the switch 4 is an operator-controlled switch for controlling merely the individual exposures, both these switches acting on the tube through the relay switch 2.

Once the limit switch 5 is open, any closing of the exposure switch 4 by the operator will complete an energizing circuit for the signal device I4 and thus indicate that the tube cannot be operated.

Should the same total time be proper for the next patient, as is frequently the case, it is obviously unnecessary that the operator readjust the stop l3. If the room be darkened he need merely again move the knob II from its zero position until it engages the stop, with assurance that the stop has not been moved from the position in which he initially set it.

What I claim is:

1. Apparatus for the purpose described, comprising an X-ray tube, operator-operated exposure switch means, time limit means, and means inter associating said tube and exposure switch means and time limit means in a manner to provide operation of said tube in successive periods responsive to said exposure switch means, to provide metering operation of said time limit means only during tube operation, and to provide operation of said time limit means to prevent said tube operation beyond a predetermined total time attained during said periods.

2. Apparatus for the purpose described, comprising an X-ray tube, operator-operated exposure switch means, time limit means, means associating said tube and exposure switch means and time limit means in a manner to provide operation of said tube in successive periods responsive to said exposure switch means, to provide metering operation of said time limit means only during tube operation, and to provide operation of said time limit means to prevent said tube operation beyond a predetermined total time attained dur ing said periods, operator-operated means for presetting said time limit means to a selected tube operating time limit, and adjustable stop means for said presetting means.

3. Apparatus for the purpose described, comprising an X-ray tube and its operating circuit, a control circuit for said operating circuit including in series an operator-operated switch, a time limit switch and motor means, a timing device arranged to be driven by said motor means, said device being arranged to open said time limit switch upon completion of the operating cycle of said timing device, and a control member for said operating circuit energized coincidently with said control circuit.

4. In apparatus having an X-ray tube, an operating circuit therefor, a relay switch in said operating circuit, time limit switch means and a synchronous driving motor therefor, a control circuit for said relay switch, an exposure switch in series relation with said time limit switch and said motor in said control circuit, and an energizing coil for said relay switch in parallel relation with said motor.

5. In apparatus having an X-ray tube, an operating circuit therefor, a relay switch in said operating circuit, time limit switch means and a synchronous driving motor therefor, a control circuit for said relay switch, an exposure switch in series relation with said time limit switch and said motor in said control circuit, an energizing coil for said relay switch in parallel relation with said motor, and signal means arranged in said control circuit to be energized when said relay switch is open while said exposure switch is closed.

EDWIN R. GOLDFIELD. 

